This invention relates generally to handling industrial rolls of web or sheet material such as large rolls of carpet, textiles, paper, plastic, and the like. More specifically, the invention relates to core chucks insertable in the cores of such rolls for gripping the cores tightly to apply driving or braking forces to the rolls as material is wound onto or drawn from the rolls.
Bulk quantities of web or sheet material are often supplied in large rolls wound about a hollow tubular core made of paperboard or plastic. When working with such rolls in a manufacturing facility, there is often a need to mount the rolls on spindles so that material can be wound onto or drawn from the rolls. For example, newspaper publishers usually draw newsprint paper from large rolls and carpet suppliers store carpet on and remove it from large carpet rolls. Many other types of web materials such as non-wovens are also stored on rolls.
When material is being wound onto a roll, it typically is necessary to rotate the core of the roll during the winding process. Conversely, when material is being drawn or from a roll for use in a manufacturing process, it usually is necessary to apply a breaking or tensioning force to the roll to keep the material taut and to prevent freewheeling of the roll and resultant spillage of material. Historically, mounting rolls of sheet and web material on a spindle to allow the application of driving or tensioning forces has been accomplished with core chucks and shafts. A core chuck is a device that is inserted in the ends of the tubular core of a roll and, through some mechanism, grips the core so that forces applied to the chuck through the spindle or shaft is transferred to the core and to the roll. A core shaft is similar to a core chuck but extends completely through the core of the roll, thus serving both as the chuck assembly and the shaft.
Many types of core chucks and core shafts are available. One simple type is known as a core plug. A typical core plug is a conical section-shaped plug made of metal or plastic with serrations or teeth formed on its conical outer surface. In use, a core plug is forced into each end of a core until it is tight. The spindle shaft is then extended through and secured to the plugs such that driving or tensioning forces applied to the shaft are transferred to the roll through the plugs. While core plugs offer the advantage of-simplicity, they nevertheless are plagued with certain inherent problems and shortcomings, primary among which is their tendency to tear and destroy cores during operation. Core plugs also tend to slip and spin out within their cores, especially when used with large heavy rolls of material such as carpet or paper rolls. Core plugs are therefore generally limited to light duty applications.
Another type of available core chuck is known as the pneumatic or air chuck. Air chucks generally are provided with plates, leaves, or lugs that overlie an inflatable bladder or bladders within the chuck. In use, air chucks are inserted into a core and their internal bladders are inflated with an external source of compressed air or fluid. Inflation of the bladders in turn urges the overlying leaves outwardly into locking frictional contact with the interior wall of the core. Air chucks are also available in the form of air shafts, which extend completely through a core and incorporate or include the spindle shaft.
While air chucks and shafts work relatively well in most material roll cores, they too have their problems and shortcomings. Key among these problems is the expense, complexity, and high maintenance costs of the chucks and shafts. In addition, air chucks are inefficient because they require an external source of compressed air or fluid, which must be maintained, and require operator intervention for inflation and deflation. Finally, when used with heavy rolls of material such as rolls of carpet or steel, air chucks tend to cause the roll to rotate a bit off center. This is because the weight of the roll compresses the portion of the bladder beneath the top leaves of the chuck, which causes a distension of the portion of the bladder beneath the bottom leaves. Accordingly, air chucks and shafts generally are not suited to situations where heavy rolls of material are to be rotated at relatively high speeds.
Another type of core chuck is the mechanical chuck. In a typical mechanical chuck, an array of lugs, bars, dogs, or leaves, or an elastic shell is mechanically urged outwardly into gripping or frictional contact with the interior wall of a roll core to couple the chuck to the core. While mechanical core chucks can also be successful, they have their own set of problems. In many mechanical chucks, for example, an array of relatively small lugs are urged outwardly and pierce the wall of the core or grip it with jaw-like projections. These aggressive locking mechanisms can cause the core to rip and tear especially under heavy loads and large forces. Most mechanical chucks engage the interior of a core at several discrete locations rather than over a large area. As a result, driving and tensioning forces are transferred to the core through relatively small areas of contact, which, again, can cause the cores to tear and be destroyed. While mechanical chucks typically are somewhat less expensive and less troublesome to use than air chucks, they nevertheless tend to have many working parts and can require periodic maintenance and part replacement. Because of their complex mechanisms, some mechanical core chucks engage in only one direction, requiring that the chucks be removed and reversed if it is desired to drive or tension a roll in the opposite direction.
Mechanical core chucks also include elastic shell chucks, wherein a rubberized or elastic shell is expanded into engagement with the interior of a roll core by an eccentric internal shaft. These types of chucks, while transferring force over a larger area, tend to loose their grip when a driving or tensioning force is temporarily removed and can be somewhat sluggish in operation because of the elasticity of the rubberized shell.
Some examples of mechanical core chucks illustrative of the types discussed above are disclosed in U. S. Pat. No. 5,490,640 of Grashorn; U.S. Pat. No. 3,337,151 of Parkinson; U.S. Pat. No. 3,811,632 of Bassett; U.S. Pat. No. 4,893,765 of Randolph; U.S. Pat. No. 5,524,849 of Dorfel et al.; U.S. Pat. No. 5,683,057 of Gangemi; and U.S. Pat. No. 5,490,640 of Miller et al. The devices of these patents exhibit one or more of the forgoing problems.
Accordingly, there exists a need for an improved core chuck that is simple to use, automatic in operation, that operates equally well in both rotational directions of a roll, does not require application of pressurized air or fluid, and that require virtually no maintenance. It is to the provision of such a core chuck that the present invention is primarily directed.
Briefly described, the present invention, in one preferred embodiment thereof, comprises an improved core chuck for coupling a roll of web material to a spindle such that driving or tensioning forces can be coupled to the roll. The chuck includes an elongated generally spool-shaped main body or mandrel having first and second ends and an outer surface. The outer surface of the mandrel is formed with a set of longitudinally extending lobes, with the preferred embodiment having a set of three or more lobes. A set of arcuate friction plates are mounted on and substantially surround the outer surface of the mandrel. Together, the friction plates form a shell around the mandrel. Each friction plate has an interior surface for engaging the longitudinally extending lobes and an exterior surface for frictionally engaging the inside surface of a core in which the chuck is disposed. The materials from which the mandrel and plates are fabricated are chosen so that the coefficient of friction between the friction plates and the outer surface of the mandrel is less than the coefficient of friction between the friction plates and the inside surface of a core.
The interior surface of each friction plate is contoured to conform to the shape of a corresponding one of the lobes and the exterior surfaces of the friction plates align to form a cylindrical outermost surface of the chuck. The friction plates are held in place on the mandrel by a pair of elastic bands extending around the friction plates and preferably nestled in aligned annular grooves formed in the plates. In this way, the friction plates are held securely to the mandrel but are nevertheless free to slide around the mandrel and expand against the elasticity of the bands. The friction plates are thus circumferentially slidable around the mandrel between first positions wherein the friction plates are disposed on respective ones of the lobes forming a shell of a first diameter and second positions wherein the friction plates span adjacent lobes forming a shell of a second diameter greater than the first diameter.
In use, a pair of chucks with friction plates in their first or retracted positions are inserted into the ends of the core of a roll of material. A shaft can then be extended through and secured to the chucks for mounting the roll on a spindle. Alternatively, in shaftless systems, the roll is mounted on a pair of spaced opposed chucks secured to a spindle and no shaft extends through the roll. In situations where material is to be drawn from the roll, the shaft or spindle is coupled to a breaking mechanism for applying a tensioning force to the roll.
As material is drawn from the roll, the roll and its core rotate relative to the chucks. Since the friction between the core and friction plates is greater than the friction between the friction plates and the mandrel, this relative rotation causes the friction plates to slide around the mandrel toward their second or expanded positions. As the friction plates slide and expand, they engage firmly against the inner surface of the core thereby frictionally locking the core to the chucks. Tensioning forces applied to the shaft are thus conveyed to the core through the chucks to prevent freewheeling of the roll as material is drawn therefrom.
When the roll is empty or needs to be removed, a slight rotation of the core in the opposite direction causes the friction plates to slide back to their retracted positions and the chucks can be removed easily from the core. Further rotation in the opposite directions causes the friction plates to slide up onto adjacent lobes to expanded positions in the opposite direction, again frictionally locking against the inner surface of the core. Thus, the chuck of this invention functions equally well in either rotational direction.
The same principles apply when relative motion between the chucks and the core is caused by a driving force applied to the shaft. This commonly occurs when material is being wound onto a core rather than being drawn from it. The relative rotational motion again locks the chucks frictionally to the core for transferring the driving force. The chuck of this invention thus is equally useful in situations where large rolls are driven for winding material around a core and to situations where a tensioning force is applied to rolls as material is drawn from the rolls. Further, since the friction plates of the chucks expand evenly, the center of rotation of the chuck remains aligned with the center of mass of the roll, preventing unbalanced rotation.
Accordingly, it is seen that an improved core chuck is now provided that successfully addresses the problems and shortcomings of the prior art. The chuck is simple in construction and operation, requires virtually no maintenance, is highly reliable, and requires no external source of compressed air or fluid for its operation. Further, the chuck cannot tear or destroy a core because its friction plates engage the inner surface of the core over a large surface area rather than with small lugs or dogs as used in many prior art chucks. These and other features, objects, and advantages of the invention will become more apparent upon review of the detailed description set forth below taken in conjunction with the accompanying drawings, which are briefly described as follows.